Method of laterally inserting an artificial vertebral disk replacement implant with curved spacer

ABSTRACT

The present invention is directed to an implant that can be placed between two adjacent vertebral bodies using a lateral insertion method. The implant is characterized as having a first end plate and a second end plate which a crossbar spacer therebetween. The crossbar spacer preferably fits within a channel on the inner surfaces of the first end plate and the second end plate, whereby the spacer allows pivots, twisting and/or rotational movement of the spine. The first end plate and the second end plate include a keel extending therefrom, whereby the keel traverses longitudinally between a first lateral side and a second opposed lateral side and is substantially perpendicular to the sagittal plane of the patient&#39;s spine.

CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/524,350, filed Nov. 21, 2003, entitled “ARTIFICIAL VERTEBRAL DISKREPLACEMENT IMPLANT WITH A SPACER AND LATERAL IMPLANT METHOD,” which isincorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Provisional Application No.60/422,039, filed Oct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISKREPLACEMENT IMPLANT WITH TRANSLATING PIVOT POINT AND METHOD,” U.S.patent application Ser. No. 10/684,669, filed Oct. 14, 2003, entitled“ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOTPOINT AND METHOD,” U.S. Provisional Application No. 60/422,011, filedOct. 29, 2002, entitled “TOOLS FOR IMPLANTING AN ARTIFICIAL VERTEBRALDISK AND METHOD,” U.S. patent application Ser. No. 10/685,134, filedOct. 14, 2003, entitled “TOOLS FOR IMPLANTING AN ARTIFICIAL VERTEBRALDISK AND METHOD,” U.S. Provisional Application No. 60/422,022, filedOct. 29, 2002, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANTWITH A SPACER AND METHOD,” U.S. patent application Ser. No. 10/685,011,filed Oct. 14, 2003, entitled “ARTIFICIAL VERTEBRAL DISK REPLACEMENTIMPLANT WITH SPACER AND METHOD,” and U.S. Provisional Application No.60/517,973, filed Nov. 6, 2003, entitled “ARTIFICIAL VERTEBRAL DISKREPLACEMENT IMPLANT WITH CROSSBAR SPACER AND LATERAL IMPLANT METHOD,”U.S. patent application Ser. No. ______, filed ______, entitled“LATERALLY INSERTABLE ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITHTRANSLATING PIVOT POINT,” (KLYCD-05007US5), U.S. patent application Ser.No. ______, filed ______, entitled “METHOD OF LATERALLY INSERTING ANARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH TRANSLATING PIVOTPOINT,” (KLYCD-05007US6), U.S. patent application Ser. No. ______, filed______, entitled “LATERALLY INSERTABLE ARTIFICIAL VERTEBRAL DISKREPLACEMENT IMPLANT WITH A CROSSBAR SPACER,” (KLYCD-05008US6), U.S.patent application Ser. No. ______, filed ______, entitled “METHOD OFLATERALLY INSERTING ARTIFICIAL VERTEBRAL DISK REPLACEMENT IMPLANT WITH ACROSSBAR SPACER,” (KLYCD-05008US7), U.S. patent application Ser. No.______, filed ______, entitled “LATERALLY INSERTABLE ARTIFICIALVERTEBRAL DISK REPLACEMENT IMPLANT WITH A SPACER,” (KLYCD-05010US4), allof which are incorporated herein by reference.

FIELD OF ART

This field of art of this disclosure is directed to an artificialvertebral disk replacement and method.

BACKGROUND

The spinal column is a biomechanical structure composed primarily ofligaments, muscles, vertebrae and intervertebral disks. Thebiomechanical functions of the spine include: (1) support of the body,which involves the transfer of the weight and the bending movements ofthe head, trunk and arms to the pelvis and legs, (2) complexphysiological motion between these parts, and (3) protection of thespinal cord and nerve roots.

As the present society ages, it is anticipated that there will be anincrease in adverse spinal conditions which are characteristic of aging.For example, with aging comes an increase in spinal stenosis (including,but not limited to, central canal and lateral stenosis), and facet jointdegeneration. Spinal stenosis typically results from the thickening ofthe bones that make up the spinal column and is characterized by areduction in the available space for the passage of blood vessels andnerves. Facet joint degeneration results from the constant load borne bythe facet joints, and the eventual wear that results. Pain associatedwith both conditions can be relieved by medication and/or surgery.

In addition, to spinal stenosis, and facet joint degeneration, theincidence of damage to the intervertebral disks is also common. Theprimary purpose of the intervertebral disk is to act as a shockabsorber. The disk is constructed of an inner gel-like structure, thenucleus pulposus (the nucleus), and an outer rigid structure comprisedof collagen fibers, the annulus fibrosus (the annulus). At birth, thedisk is 80% water, and then gradually diminishes with time, becomingstiff. With age, disks may degenerate, and bulge, thin, herniate, orossify. Additionally, damage to disks may occur as a result disease,trauma or injury to the spine.

The damage to disks may call for a range of restorative procedures. Ifthe damage is not extensive, repair may be indicated, while extensivedamage may indicate full replacement. Regarding the evolution ofrestoration of damage to intervertebral disks, rigid fixation proceduresresulting in fusion are still the most commonly performed surgicalintervention. However, trends suggest a move away from such procedures.Currently, areas evolving to address the shortcomings of fusion forremediation of disk damage include technologies and procedures thatpreserve or repair the annulus, that replace or repair the nucleus, andthat advance implants for total disk replacement. The trend away fromfusion is driven both by issues concerning the quality of life for thosesuffering from damaged intervertebral disks, as well as responsiblehealth care management. These issues drive the desire for proceduresthat are minimally invasive, can be tolerated by patients of all ages,especially seniors, and can be performed preferably on an out patientbasis.

Most recently, there has been an increased interest in total diskreplacement technology. A number of artificial disks are beginning toappear in the medical device marketplace. These artificial disks varygreatly in shape, design and functionality. With these devices go toolsand methods for insertion between vertebrae thereof. Though currentlythe most common method of insertion of disk replacement implants is theanterior approach, other surgical procedures, such as the lateralapproach, are evolving.

Accordingly, there is a need in the art for innovation in technologiesand methods that advance the art in the area of minimally invasiveintervertebral disk replacement. This not only enhances the quality oflife for those suffering from the condition, but is responsive to thecurrent needs of health care management.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side perspective view of an embodiment of the assembledimplant 100. FIG. 1B is an alternative side perspective view of anembodiment of the assembled implant 100.

FIG. 2A and FIG. 2B show perspective views of the first and second innersurfaces of the first end plate and the second end plate of anembodiment of implant 100. FIG. 2 c through FIG. 2F show cross-sectionalviews of the first end plate and the second end plate of an embodimentof implant 100.

FIG. 3A is a perspective view of a spacer of an embodiment of implant100. FIG. 3B and FIG. 3 c are cross-sections of the spacer of anembodiment of implant taken at 90° angles respective to each other.

FIG. 4A is a cross-section of an embodiment of implant 100 taken along aplane parallel to the sagittal plane. FIG. 4B is a cross-section of anembodiment of implant corresponding to a plane parallel to the locationof the coronal plane, or perpendicular to the sagittal plane of thevertebrae after implant 100 has been inserted.

FIG. 5A and FIG. 5B show perspective views of the first and second innersurfaces of the first end plate and the second end plate of anotherembodiment of implant 100. FIG. 5 c is a cross-section of the embodimentof implant 100 taken along a plane parallel to the sagittal plane. FIG.5D is a cross-section of the embodiment of implant 100 corresponding toa plane parallel to the location of the coronal plane, or perpendicularto the sagittal plane of the vertebrae after implant 100 has beeninserted.

FIG. 6 is a block diagram showing the method steps for the lateralimplantation of an embodiment of the disclosed the disclosed implant.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use what is disclosed. Various modifications to theembodiments described will be readily apparent to those skilled in theart, and the principles defined herein can be applied to otherembodiments and applications without departing from the spirit and scopeof what is disclosed and defined by the appended claims. Thus, what isdisclosed is not intended to be limited to the embodiments shown, but isto be accorded the widest scope consistent with the principles andfeatures disclosed herein. To the extent necessary to achieve a completeunderstanding of what is disclosed herein, the specification anddrawings of all patents and patent applications cited in thisapplication are incorporated herein by reference.

FIG. 1A shows an embodiment of implant 100. The designations, “A” foranterior, “P” for posterior, “RL” for right lateral, and “LL” for leftlateral are given in the drawings for spatial orientation. Thesedesignations give the relationship of all faces of implant from thesuperior perspective; i.e. looking down the axis of the spine. Implant100 has a first end plate, or upper end plate 110 that is configured tomate with a first vertebra, and a second end plate, or lower end plate120 that is configured to mate with a second vertebra. A third part 130that sits between the first end plate 110 and the second end plate 120is also provided. The third part 130 acts as a spacer between the firstend plate 110 and the second end plate 120 and facilitates pivotal orrotational and also twisting movement of the first end plate 110 and thesecond end plate 120, relative to each other. The third part 130, thespacer, is dimensioned so that it has a curved or convex upper surfaceand a curved or convex lower surface, as discussed in more detail below.

The upper end plate 110 has a first outer surface 112 from which a firstkeel 114 extends with a first set of teeth 115. In one embodiment, whenimplant 100 is inserted between vertebrae, the first keel 114 extendslongitudinally across the first outer surface 112, about perpendicularto the sagittal plane of the spine. In another embodiment, the firstkeel 114 extends longitudinally only partially across the first outersurface 112, about perpendicular to the sagittal plane of the spine. Theteeth in the two embodiments with complete or partial extension of thekeel across the first outer surface 112 of the upper end plate 110,point towards the left lateral face of implant 100 when the embodimentis meant to be put into a slot in a vertebral body from the left lateralapproach to the spine. This orientation is shown in FIG. 1A and FIG. 1B,for example. Alternatively, the teeth 115 point towards the rightlateral face of implant 100 when the embodiments are meant to be putinto a slot in a vertebral body from the right lateral approach to thespine.

The first outer surface 112 abuts the vertebral body when implant 100 isinserted between vertebrae. The first keel 114 extends into thevertebral body to anchor implant 100 into position, and is perpendicularto the median sagittal plane of the spine, in which extension andflexion occur. The first keel 114 in this orientation offers substantialstability during extension and flexion for implant 100 inserted betweenthe vertebrae of a patient. Additionally, the first keel 114 in thisembodiment is aligned with and supports the lateral axis of articulationof implant 100 perpendicular to the sagittal plane of the spine. Thefirst inner surface 116 engages the spacer 130 of implant and opposesthe second end plate 120. The first inner surface 116 can form a planarsurface that is parallel to the first outer surface 112, or can form aplanar surface that is not parallel to the first outer surface 112.

The lower end plate 120 has a second outer surface 122 from which a keelsecond 124 extends with a second set of teeth 125. In one embodiment,when implant 100 is inserted between vertebrae, the second keel 124 isabout perpendicular to the sagittal plane of the spine. As describedabove for the first upper end plate 110, in one embodiment, the secondkeel 124 extends longitudinally across the second outer surface 122,while in another embodiment, the second keel 124 extends longitudinallypartially across the second outer surface 122. Similarly, the teeth inthe two embodiments with complete or partial extension of the keelacross the second outer surface 122 of the lower end plate 120 pointtowards the left lateral face of implant 100 when the embodiment ismeant to be put into a slot in a vertebral body from the left lateralapproach to the spine. Alternatively, the teeth 125 point towards theright lateral face of implant 100 when the embodiments are meant to beput into a slot in a vertebral body from the right lateral approach tothe spine.

The second outer surface 122 abuts the vertebral body when implant 100is inserted. The second keel 124 extends into the vertebral body toanchor implant 100 into position, and is perpendicular to the mediansagittal plane of the spine, in which extension and flexion occur. Thesecond keel 124 in this orientation offers substantial stability duringextension and flexion for implant 100 inserted between the vertebrae ofa patient. Additionally, the second keel 124 in this embodiment isaligned with and supports the lateral axis of articulation of implant100 perpendicular to the sagittal plane of the spine. The second innersurface 126, engages the spacer 130 of implant and opposes the first endplate 110. The second inner surface 126 can form a planar surface thatis parallel to the second outer surface 122, or can form a planarsurface that is not parallel to the second outer surface 122.

The lateral orientation of the first keel 114 and the second keel 124allow the implant 100 to be inserted into the spine using anadvantageous lateral approach as opposed to an anterior or posteriorapproach. In comparison to a posterior insertion approach in which thespinal nerves can be substantially disturbed, the spinal nerves arebypassed and relatively undisturbed when the implant 100 is insertedlaterally between the vertebral bodies from the side of the spine.Although an anterior insertion approach has its benefits, the lateralinsertion approach can allow the present implant 100, and associatedimplantation tools, to be inserted into the spine with less disturbanceof the patient's internal organs. This can translate into less time andrisk associated with preparing the spine for insertion as well asinserting the implant itself into the spine. Further, the laterallyoriented first and second keels 114, 124 offer substantial stability tothe vertebral bodies during extension, flexion and lateral bending ofthe spine.

The first inner surface 116 of the first end plate 110 can be parallelto the second inner surface 126 of the second end plate 120 when implant100 is assembled and is in a neutral position (i.e., the position wherethe first end plate 110 has not rotated relative to the second end plate120). Alternatively, the first inner surface 116 of the first end plate110 can be non-parallel to the planar surface of the second innersurface 126 of the second end plate 120 when implant 100 is assembledand in a neutral position. This non-parallel orientation of the firstend plate 110 and the second end plate 120 allows the plates to pivot toa greater degree with respect to each other. Additionally, other factorssuch as the height and position of the spacer 130, can also be adjustedin order to increase the degree that the first end plate 110 and thesecond end plate 120 can pivot relative to each other.

The embodiments shown in FIG. 1 a and FIG. 1 b illustrate the first andsecond keels 114,124, which include ports 148,152, respectively, thatfacilitate bone ingrowth. For example, bone from the vertebral bodiescan grow thorough the ports 148,152, and aid in securing the first andsecond keels 114,124 and the implant 100 with respect to the vertebralbodies. In addition, surfaces defined by the first and second keels114,124 and the first and second outer surfaces 112, 122 of implant 100can be roughened in order to promote bone ingrowth into these definedsurfaces of implant 100. In another embodiment the ports 148,152, thefirst and second keels 114,124, and the first and second outer surfaces112, 122 of implant 100 can be coated with materials that promote bonegrowth such as for example bone morphogenic protein, BMP, or structuralmaterials such as hyaluronic acid, HA, or other substance which promotesgrowth of bone relative to and into the keel, keel ports, and otherexternal surfaces of the implant 100.

When implant 100 is inserted between vertebrae the planar surfacescorresponding to the first and second outer surfaces 112, 122 and thefirst and second inner surfaces 116, 126 of the first and second endplates 110, 120 lie within, or substantially within, the axial plane ofthe body of the patient. Similarly, the first and second keels 114, 124are aligned in the axial plane, or perpendicular to the sagittal planeof the vertebrae.

FIG. 1B shows an alternative perspective view of implant 100 shown inFIG. 1A. Again, implant 100 has a first or upper end plate 110 that isconfigured to mate with a first vertebra and a second or lower end plate120 that is configured to mate with a second vertebra. The first andsecond keels 114,124 extend into the vertebral bodies to anchor implant100 into position, and are perpendicular to the median sagittal plane ofthe spine, in which extension and flexion occur. The first and secondkeels 114,124 in this orientation offer substantial stability duringextension and flexion for implant 100 inserted between the vertebrae ofa patient. Additionally, the first and second keels 114,124 in thisembodiment are aligned with and support the axis of articulation ofimplant 100 defined by an RL to LL orientation. The axis of articulationof implant 100 defined by an RL to LL orientation will be discussed inmore detail below. The spacer 130 separates the first end plate 110 fromthe second end plate 120. As evidenced from the perspective view of FIG.1B, the perimeter shape of the upper and lower end plates 110,120 can beconfigured to correspond to the perimeter shape of a vertebral disk. Aswill be appreciated by those of ordinary skill in the art, the perimetershape of the upper end plate 110 and the lower end plate 120 can be thesame.

FIG. 2 a shows a perspective view of an embodiment of the first innersurface 116 of the first or upper end plate 110 of implant 100. Thefirst inner surface 116 of the upper end plate 110 has a first socket orfirst cavity 210 formed therein. In one embodiment, the first socket 210has a concave hemi-cylindrical surface. In this embodiment, the firstsocket 210 includes the shallow concave surface 211 with first ends213,215 that are substantially perpendicular to the first inner surface116. Also indicated in FIG. 2 a are two axes, 217,219. The first upperaxis 217 intersects the first upper plate 110 in an RL to LLorientation. The second upper axis 219 is perpendicular to the firstupper axis 217, and intersects the upper plate 110 in an A to Porientation. The first socket 210 allows the first end plate 110 topivot or rotate on spacer 130, about a first upper axis 217 that isabout perpendicular to the first ends 213,215. The ends 213,215 blockmotion of the spacer 130 about the second upper axis 219, perpendicularto the first upper axis 217. In this embodiment, it is noted that thefirst and second keels 114,124 are aligned with and support the firstupper axis 217, which is an axis of articulation for first end plate 110about the spacer 130 for this embodiment, and is an axis that is aboutperpendicular to the sagittal plane of the spine.

As can be seen in FIG. 2 a, the first socket 210 in this embodimentincludes first ends 213,215 that have crests 233,235 respectively. Thecrests 233,235 project into the first socket 210. Additionally, concavesurface 211 has edges 234,236 with crests 237, 239, respectively. Thecrests 233, 235, 237, and 239 allow a loose fit between the spacer 130and the first socket 210, which will be disused in more detail below.

FIG. 2 b shows a perspective view of an embodiment of the second orlower end plate 120 of implant 100. The second inner surface 126 of thelower end plate 120 has a second socket or second cavity 240 formedtherein. In one embodiment, the second socket 240 has a concavehemi-cylindrical surface. In this embodiment, the second socket 240includes the shallow concave surface 241 with second ends 243,245 thatare substantially perpendicular to the second inner surface 126. Alsoindicated in FIG. 2 b are two axes, 247,249. The first lower axis 247intersects the first lower plate 120 in an A to P orientation. Thesecond lower axis 249 is perpendicular to the first lower axis 247, andintersects the lower plate 120 in an RL to LL orientation. As will bedescribed later with respect to the spacer 130, the second socket 240allows the second end plate 120 to pivot or rotate on spacer 130, aboutthe first lower axis 247 that is about perpendicular to the second ends243,245. The ends 243,245 block motion of the spacer 130 about thesecond lower axis 249, perpendicular to the first lower axis 247. Inthis embodiment, it is noted that the second lower axis 249 is aboutparallel with first upper axis 217. As previously mentioned, the firstand second keels 114,124 are aligned with and support the first upperaxis 217, which is an axis of articulation of the upper end plate 110about the spacer 130 for this embodiment, and is an axis that is aboutperpendicular to the sagittal plane of the spine, as is second loweraxis 249. Further, the first lower axis 247 is an axis of articulationof the lower end plate 120 about the spacer 130, and the first loweraxis 247 is perpendicular to the first upper axis 217.

The fit of the spacer in the first socket 210 and the second socket 240can be loose so that the spacer allows the first end plate 110 to beable to twist somewhat relative to the second plate 120. This twistingaction would generally be about an axis that is perpendicular to thefirst and second inner surfaces 116,126 of the first and second endplates 110,120, respectively. Thus, implant 100 of this embodimentallows the spine to have movement in three orthogonal degrees offreedom, namely (1) forward and backward bending movement, (2) lateralside-to-side bending, and (3) twisting movement. It is to be understoodthat the second socket 240 in the lower end plate 120 can also have thesame design as the first socket 210 in the upper end plate 110 with anincrease in the amount of twisting movement afforded by implant 100. Asis noted previously herein, loose fit generally between one or both offirst socket 210 and second socket 240 and the spacer 130 can allow fortwisting motion. Further the spacer 130 can also be made with crests onthe curved surfaces and on the ends in order to afford similar twistingmotion. In other embodiments, the fit can be tighter in order torestrict such twisting action.

Turning now to FIG. 2 c through FIG. 2 f, the cross-sections of theupper and lower end plates 110,120 of an embodiment of implant 100 areshown. FIG. 2 c illustrates the first dimension 212 of the first socket210, and FIG. 2 d illustrates the second dimension 214 of the firstsocket 210. The first dimension 212 and the second dimension 214 of thefirst socket 210 are perpendicular to each other. FIG. 2 e illustratesthat the first dimension 242 of the second socket 240, and FIG. 2 fillustrates the second dimension 244 of the second socket 240. The firstdimension 242 and the second dimension 244 of the second socket 240 areperpendicular to each other. FIGS. 2 c and 2 e are a cross-section takenalong a plane that would correspond to a plane that is parallel to themedian sagittal plane of the body after implant was inserted. FIG. 2 dand FIG. 2 f are a cross-section taken along a plane that wouldcorrespond to a plane that is parallel to the frontal (coronal) plane ofthe body after implant 100 was inserted.

For one embodiment, relative dimensions of the first and second sockets210,240 are indicated in FIG. 2 c through FIG. 2 f. As previouslydiscussed, the first and second outer surfaces 112,122 of the first andsecond end plates 110,120 are configured to contact vertebral bodieswhen implant 100 is inserted between vertebrae. The first and secondouter surfaces 112,122 have first and second keels 114,124 that extendinto the vertebral body when implant 100 is inserted between vertebrae.The first and second inner surfaces 116,126 of the upper and lower endplates 110,120 have first and second sockets 210,240 formed therein.

In FIG. 2 c, the first socket 210 has a first dimension 212. In thefirst dimension 212, the first socket 210 is concave such that it iscurved like the inner surface of a cylinder. In FIG. 2 d, the seconddimension 214 is in the form of a trough or “flattened-U” with apreviously indicated concave bottom surface 211 and two ends orsidewalls 213, 215. As shown in FIG. 2 d, the ends or sidewalls 213, 215are parallel to each other and perpendicular to the bottom surface 211.However, as will be appreciated by those of ordinary skill in the art,the ends or sidewalls 213, 215 can be formed at an angle relative toeach other without departing from the scope of what is disclosed.

In FIG. 2 e, the second socket 240 has a first dimension 242. The firstdimension 242 is in the form of a trough or “flattened-U” with a bottomconcave surface 241 and two ends or sidewalls 243,245. As shown in FIG.2 f, the ends or sidewalls 243, 245 are parallel to each other andperpendicular to the bottom surface 241. However, as will be appreciatedby those of ordinary skill in the art, the ends or sidewalls 243, 245can be formed at an angle relative to each other without departing fromthe scope of what is disclosed. In FIG. 2 f, the second dimension 242 ofthe second socket 240 is concave such that it is curved like the innersurface of a cylinder.

As previously mentioned, FIG. 2 c and FIG. 2 d are oriented toillustrate that the first dimension 212 shown in FIG. 2 c and the seconddimension 214 shown in FIG. 2 d are perpendicular to each other, whileFIG. 2 e and FIG. 2 f illustrate that the first dimension 242 isperpendicular to second dimension 244. Further, the curved firstdimension 212 of FIG. 2 c is oriented perpendicularly to the curvedsecond dimension 244 of FIG. 2 f, while the trough dimension 214 of FIG.2 d is oriented perpendicularly to the trough dimension 242 of FIG. 2 e.It is noted that in FIGS. 2 c through 2 f that the first inner andsecond inner surfaces 116,126 of the first and second plates 110,120 arenot parallel as shown in FIG. 1 a and FIG. 1 b, for example. In FIGS. 2c through 2 f the surfaces slope away from the first and second sockets210,240, respectively, in order to provide for a larger range of motionbetween the first and second plates.

In FIG. 3 a, the spacer 130 is depicted in perspective view. The spacer130 is dimensioned so that it has a curved or convex upper surface 310and a curved or convex lower surface 320, respectively, correspondingwith the opposing concave surfaces in the upper end plate 110 and thelower end plate.

As shown in FIG. 3 a, the curved upper surface 310 is bordered along itscurved edge by a pair of first sides 312, 314 that are parallel to eachother and along its flat edge by a pair of second sides 316, 318 thatare parallel to each other and perpendicular to the pair of first sides312, 314. The orientation of the pair of first sides 312, 314 to thepair of second sides 316, 318 is such that the curved upper edges 322,324 of the first sides 312, 314 extend toward the ends of the flat edges321, 323 of the pair of second sides 316, 318. The curved lower edges326, 328 extend to meet the ends of the flat edges 325, 327 of the firstsides 312, 314.

FIG. 3 b and FIG. 3 c show cross-sections of the spacer 130, shown inFIG. 3 a. The cross-section of FIG. 3 b is taken at a 90° angle from thecross-section shown in FIG. 3 c. FIG. 3 b is taken through a planeparallel to the ends 312, 314 and FIG. 3 c is taken through a planeparallel to ends 316, 318. The spacer 130 has a concave upper surface310 and a concave lower surface 320 and pairs of parallel sides 312, 314and 314, 318.

FIG. 4 a and FIG. 4 b show sections for an embodiment of implant 100.FIG. 4 a shows a cross-section of implant 100 in its assembled conditiontaken along a plane that would correspond to a plane that is parallel tothe median sagittal plane of the body of a patient after implant 100 wasinserted. FIG. 4 b shows a cross-section of implant 100 in its assembledcondition taken at 90° from the cross-section shown in FIG. 4 a, whichis parallel to the frontal (coronal) plane, or perpendicular to thesagittal plane of the body of a patient after implant 100 was inserted.The implant 100 has a first upper end plate 110 that is configured tomate with a first vertebra and a second lower end plate 120 that isconfigured to mate with a second vertebra. The spacer 130 sits betweenthe upper end plate 110 and the lower end plate 120. As previouslymentioned, the first upper axis 217 is an axis of articulation for firstend plate 110 about the spacer 130 for this embodiment, while the firstlower axis 247 is an axis of articulation of the lower end plate 120about the spacer 130. Further, first upper axis 217 is perpendicular tothe first lower axis 247. FIG. 4 a, in particular, indicates how thefirst and second keels, 114,124, are aligned with and support thelateral axis of articulation defined by the first upper axis 217. Thefirst and second keels 114,124 in this orientation offers substantialstability during extension and flexion for implant 100 inserted betweenthe vertebrae of a patient. As in all of the embodiments describedherein, the keels are about perpendicular to the sagittal plane of thebody of a patient and suitable for lateral insertion into the spine of apatient.

FIG. 5 a through FIG. 5 c show representations for an another embodimentof implant 100. FIG. 5 a and FIG. 5 b show the first and second innersurfaces, 116,126, of the first and second endplates of anotherembodiment of implant 100. It should be noted that this additionalembodiment of Implant 100 has the features described previouslydescribed for FIG. 2 a and FIG. 2 b. Similarly, FIG. 5 c and FIG. 5 dare sections that are analogous to the sections of a first embodimentshown for FIG. 4 a and FIG. 4 b, respectively.

FIG. 5 a shows a perspective view of an embodiment of the first innersurface 116 of the first or upper end plate 110 of implant 100. Thefirst inner surface 116 of the upper end plate 110 has a first socket orfirst cavity 210 formed therein. In the embodiment of FIG. 5 a, thefirst socket 210 has a concave hemispherical surface. Indicated in FIG.5 a are two axes, 217,219. The first upper axis 217 intersects the firstupper plate 110 in an RL to LL orientation. The second upper axis 219 isperpendicular to the first upper axis 217, and intersects the upperplate 110 in an A to P orientation. The two axes intersect at first, orupper point 119. The first socket 210 allows the first end plate 110 topivot or rotate on spacer 130 about the first point 119. FIG. 5 b showsa perspective view of an embodiment of the second inner surface 126 ofthe second or lower end plate 120 of implant 100. The second innersurface 126 of the lower end plate 120 has a second socket or firstcavity 240 formed therein. In the embodiment of FIG. 5 b, the secondsocket 240 has a concave hemispherical surface. Indicated in FIG. 5 bare two axes, 247,249. The first lower axis 247 intersects the second,or lower plate 120 in an RL to LL orientation. The second lower axis 249is perpendicular to the first upper axis 247, and intersects the lowerplate 120 in an A to P orientation. The two axes intersect at second, orlower point 121. The second socket 240 allows the second lower end plate120 to pivot or rotate on spacer 130, about the lower point 121.

In the alternative embodiment shown in FIG. 5 a and FIG. 5 b, it isnoted that the first and second keels 114,124 are aligned with andsupport the first and second points and 119, 121, which are an points ofarticulation for first end plate 110 and the second end plate,respectively about the spacer 130 for this embodiment. The keels areoriented so as to be about perpendicular to the sagittal plane of apatient when the implant is inserted using a lateral approach.

FIG. 5 c shows a cross-section of implant 100 in its assembled conditiontaken along a plane that would correspond to a plane that is parallel tothe median sagittal plane of the body of a patient after implant 100 wasinserted. FIG. 5 d shows a cross-section of implant 100 in its assembledcondition taken at 90° from the cross-section shown in FIG. 5 c., whichis parallel to the frontal (coronal) plane, or perpendicular to thesagittal plane of the body of a patient after implant 100 was inserted.The implant 100 has a first upper end plate 110 that is configured tomate with a first vertebra and a second lower end plate 120 that isconfigured to mate with a second vertebra. The spacer 130 sits betweenthe upper end plate 110 and the lower end plate 120. As previouslymentioned, the first and second upper axes 217,219 define a first pointof articulation for first end plate 110 about the spacer 130 for thisembodiment, while the first and second lower axes 247,249 define asecond point of articulation of the lower end plate 120 about the spacer130. FIG. 5 c and FIG. 5 d indicate how the first and second keels,114,124, are aligned with and support the first and second points ofarticulation 119,121. The first and second keels 114,124 in thisorientation offer substantial stability during extension and flexion forimplant 100 inserted between the vertebrae of a patient.

It is to be understood that the embodiments of the disclosed implant canbe made of medical grade titanium, stainless steel or cobalt chrome.Other materials that have appropriate structural strength and that aresuitable for implantation into a patient can also be used.

Alternatively, the spacer 130 can be made out of a polymer, and morespecifically, the polymer is a thermoplastic with the other componentsmade of the materials specified above. Still more specifically, thepolymer is a polyketone known as polyetheretherketone (PEEK). Still morespecifically, the material is PEEK 450G, which is an unfilled PEEKapproved for medical implantation available from Victrex of Lancashire,Great Britain. (Victrex is located at www.matweb.com or see Boedekerwww.boedeker.com). Other sources of this material include Gharda locatedin Panoli, India (www.ghardapolvmers.com). The spacer 130 can be formedby extrusion, injection, compression molding and/or machiningtechniques. This material has appropriate physical and mechanicalproperties and is suitable for carrying and spreading the physical loadbetween the spinous process. Further in this embodiment, the PEEK hasthe following additional approximate properties: Property Value Density1.3 g/cc Rockwell M  99 Rockwell R 126 Tensile Strength  97 Mpa Modulusof Elasticity 3.5 Gpa Flexural Modulus 4.1 Gpa

It should be noted that the material selected may also be filled. Forexample, other grades of PEEK are also available and contemplated, suchas 30% glass-filled or 30% carbon-filled, provided such materials arecleared for use in implantable devices by the FDA, or other regulatorybody. Glass-filled PEEK reduces the expansion rate and increases theflexural modulus of PEEK relative to that which is unfilled. Theresulting product is known to be ideal for improved strength, stiffness,or stability. Carbon-filled PEEK is known to enhance the compressivestrength and stiffness of PEEK and lower its expansion rate.Carbon-filled PEEK offers wear resistance and load carrying capability.

The spacer can also be comprised of polyetherketoneketone (PEKK). Othermaterial that can be used include polyetherketone (PEK),polyetherketoneether-ketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK), and, generally, apolyaryletheretherketone. Further, other polyketones can be used as wellas other thermoplastics.

Reference to appropriate polymers that can be used in the spacer can bemade to the following documents, all of which are incorporated herein byreference. These documents include: PCT Publication WO 02/02158 A1,dated Jan. 10, 2002, entitled “Bio-Compatible Polymeric Materials;” PCTPublication WO 02/00275 A1, dated Jan. 3, 2002, entitled “Bio-CompatiblePolymeric Materials;” and, PCT Publication WO 02/00270 A1, dated Jan. 3,2002, entitled “Bio-Compatible Polymeric Materials.”

In operation, implant 100 enables a forward bending movement and arearward bending movement by sliding the upper end plate 110 forward andbackward over the spacer 130 relative to the lower end plate 120. Thismovement is shown as rotation about the axis 217 in FIG. 4 a and FIG. 4c.

The implant 100 enables a right lateral bending movement and a leftlateral bending movement by sliding the lower end plate 120 side-to-sideover the spacer 130 relative to upper end plate 110. This movement isshown as rotation about the axis 219 in FIG. 4 b and FIG. 4 d.Additionally, with a loose fit between the first end plate, the secondend plate and the spacer, rotational or twisting motion along an axisthat is along the spine and perpendicular to the first and second platesis accomplished.

FIG. 6 is a block diagram showing the basic steps of the method oflaterally inserting the implant 100. First the spine is exposed througha lateral access 610, then the intervertebral disk is removed ifnecessary laterally 620. The implant is then inserted laterally 630between two vertebrae and the wound is closed 640. This procedure can befollowed for either a left lateral approach or right lateral approach.For a left lateral approach, the teeth 115,125 of upper and lower keels114, 124 would be pointed towards the left lateral face of the device inorder to aid in retaining implant 100 in place. For a right lateralapproach, the teeth would point towards the right lateral face of thedevice.

Additional steps, such as cutting channels into the vertebral bodies toaccept the first and second keels 114,124 of the first and second endplates 110,120 and assembling implant 100 by inserting the spacer 130between the upper and lower end plates 110,120 prior to installation canalso be performed without departing from the scope of what is disclosed.

It is to be appreciated that although the first and second plates aredepicted as having concave cavities and the spacer is depicted as havingtwo convex surfaces that are oriented about perpendicular to each other,that other embodiments the disclosed implant can have otherconfigurations. For example, the first and second plates can have convexprotrusions, such as, for example, cylindrical protrusions that areshaped to mate with concave surfaces of a spacer, with the concavesurfaces of the spacer oriented about perpendicular to each other. Inthis embodiment, the convex protrusions of the first and the secondplates could preferably each have a pair of parallel side walls thatwould act as the side walls in the depicted embodiments in order toblock motion of the spacer. Also, it is to be appreciated that in stillanother embodiment, the spacer can have upper and lower truncated convexspherical surfaces with two pairs of side walls, instead of cylindricalsurfaces with side walls, and be in the scope and spirit of what isdisclosed herein. In this embodiment, each of the first and secondplates would have truncated concave spherical surfaces with a pair ofside walls. In still a further embodiment, each of the first and secondplates could have spherical protrusions with a pair of side walls andthe spacer could have first and second spherical concave surfaces withtwo pairs of side walls joining the first and second spherical concavesurfaces. Still alternatively, the first end plate can have a concavesurface and blocking side walls and the mating portion of the spacer canbe convex with the second plate having a convex protrusion with themating portion of the spacer, or being concave, with blocking sidewalls.

What has been disclosed herein has been provided for the purposes ofillustration and description. It is not intended to be exhaustive or tolimit what is disclosed to the precise forms described. Manymodifications and variations will be apparent to the practitionerskilled in the art. What is disclosed was chosen and described in orderto best explain the principles and practical application of theembodiments described herein, thereby enabling others skilled in the artto understand the various embodiments and various modifications that aresuited to the particular use contemplated. It is intended that the scopeof what is disclosed be defined by the following claims and theirequivalence.

1. A method of inserting an intervertebral implant comprising the stepsof: a. accessing a lateral side of adjacent vertebral bodies; b. cuttinga receiving channel into a vertebral body, wherein the receiving channelextends between a first lateral end of the vertebral body and a secondlateral end of the vertebral; and c. inserting an implant into thereceiving channel.
 2. The method of claim 1 wherein the implant includesa spacer having opposed first and second curved surfaces orientedperpendicular to one another.
 3. The method of claim 1 wherein theimplant includes a spherical spacer within.
 4. The method of claim 1wherein the step of inserting further comprises inserting a keel of theimplant into the receiving channel.
 5. The method of claim 1 wherein thestep of inserting further comprises inserting a keel of the implant intothe receiving channel, wherein the keel is oriented perpendicular to thesagittal plane of the vertebral body when inserted therein.
 6. Themethod of claim 4 wherein the keel further comprises a plurality ofteeth each having an angled side facing the receiving channel when theimplant is inserted therein.
 7. The method of claim 1 wherein theimplant is inserted into the receiving channel from a lateral approach.8. The method of claim 1 wherein the step of cutting further comprisescutting a first receiving channel into an upper vertebral body andcutting a second receiving channel into a lower vertebral body.
 9. Themethod of claim 8 wherein the step of inserting further comprisesinserting a first keel of the implant into the first receiving channeland inserting a second keel of the implant into the second receivingchannel.
 10. The method of claim 1 further comprising assembling theimplant prior to inserting the implant into the receiving channel. 11.The method of claim 1 further comprising assembling the implantsubsequent to inserting the implant into the receiving channel.
 12. Themethod of claim 1 further comprising assembling the implant including:a. selecting a first end plate having a first keel extending from afirst outer surface between a first lateral end and a second lateralend; b. selecting a second end plate having a second keel extending froma second outer surface between a first lateral end and a second lateralend; and c. coupling the spacer to the first end plate and the secondend plate.
 13. The method of claim 12 wherein coupling the spacer to thefirst and second end plates further comprises: a. inserting the firstcurved surface of the spacer into a first socket in the first end plate;and b. inserting the second curved surface of the spacer into a secondsocket in the second end plate.
 14. A method of attaching an artificialdevice between adjacent vertebral bodies of a spine comprising: a.cutting a keel receiving channel into a vertebral body, wherein the keelreceiving channel is substantially perpendicular to the sagittal planeof the spine; and b. inserting a keel of an artificial device into thekeel receiving channel.
 15. The method of claim 14 wherein theartificial device includes a spacer having opposed first and secondcurved surfaces oriented perpendicular to one another.
 16. The method ofclaim 14 wherein the artificial device includes a spherical spacerwithin.
 17. The method of claim 14 wherein the keel is orientedperpendicular to the sagittal plane of the spine when inserted therein.18. The method of claim 14 wherein the keel further comprises aplurality of teeth each having an angled side facing the keel receivingchannel when the artificial device is inserted therein.
 19. The methodof claim 14 wherein the artificial device is inserted into the keelreceiving channel from a lateral approach.
 20. The method of claim 14wherein the step of cutting further comprises cutting a first keelreceiving channel into an upper vertebral body and cutting a second keelreceiving channel into a lower vertebral body.
 21. The method of claim20 wherein the step of inserting further comprises inserting a firstkeel of the implant into the first keel receiving channel and insertinga second keel of the implant into the second keel receiving channel. 22.The method of claim 14 further comprising assembling the artificialdevice prior to inserting the keel of the artificial device into thereceiving channel.
 23. The method of claim 14 further comprisingassembling the artificial device subsequent to inserting the keel of theartificial device into the receiving channel.
 24. The method of claim 14further comprising assembling the artificial device including: a.selecting a first end plate having a first keel extending from a firstouter surface and a first socket in a first inner surface; b. selectinga second end plate having a second keel extending from a second outersurface and a second socket in a second inner surface; and c.positioning a first curved surface of the spacer in the first socket anda second curved surface of the spacer in the second socket.
 25. Themethod of claim 24 wherein the first curved surface and the secondcurved surface are oriented perpendicular to one another.
 26. A methodof inserting an implant comprising: a. accessing a lateral side of anupper vertebral body and a lower vertebral body; b. cutting a first keelreceiving channel into the upper vertebral body, wherein the first keelreceiving channel extends between a first lateral side and a secondlateral side of the vertebral body; c. cutting a second keel receivingchannel into the lower vertebral body, wherein the second keel receivingchannel is substantially parallel to the first keel receiving channel;and d. inserting a first keel of an implant into the first keelreceiving channel and a second keel of the implant into the second keelreceiving channel, wherein the implant includes a spacer having opposingfirst and second curved surface oriented perpendicular to one another.27. The method of claim 26 wherein the first and second keels areoriented substantially perpendicular to the sagittal plane of thevertebral bodies when inserted therein.
 28. The method of claim 26further comprising assembling the implant prior to inserting the implantbetween the upper and lower vertebral bodies.
 29. The method of claim 26further comprising assembling the implant subsequent to inserting theimplant between the upper and lower vertebral bodies.
 30. The method ofclaim 26 wherein the first keel further comprises a plurality of teetheach having an angled side facing the keel receiving channel when theimplant is inserted therein.
 31. The method of claim 26 wherein thesecond keel further comprises a plurality of teeth each having an angledside facing the keel receiving channel when the implant is insertedtherein.
 32. The method of claim 26 wherein the implant is inserted intothe first and second keel receiving channel from a lateral approach. 33.The method of claim 26 further comprising assembling the implantincluding: a. selecting a first end plate having the first keelextending from a first outer surface and a first socket in a first innersurface; b. selecting a second end plate having the second keelextending from a second outer surface and a second socket in a secondinner surface; and c. positioning a spacer between the first end plateand the second end plate wherein the first curved surface is positionedin the first socket and the second curved surface is positioned in thesecond socket.
 34. A method of inserting an intervertebral implantcomprising: a. accessing an intervertebral space; b. cutting a receivingchannel into at least one vertebral body, wherein the keel receivingchannel extends between a first lateral side and a second lateral sideof the vertebral body; and c. inserting at least a portion of an implantinto the receiving channel, wherein the implant is adapted to include aspacer therein having opposing first and second curved surfaces orientedperpendicular to one another.
 35. A method of inserting anintervertebral implant in a spine comprising: a. preparing an affectedarea of the spine to receive the implant; and b. inserting a keel of animplant into the affected area, wherein the keel extends between a firstlateral end and a second lateral end of the implant, the implant havingopposing first and second curved surfaces oriented perpendicular to oneanother.
 36. A method of inserting an intervertebral implant in a spinecomprising: a. preparing an affected area of the spine to receive theimplant; and b. inserting a keel of an implant into the affected areafrom a lateral approach, wherein the implant has a spacer havingopposing first and second curved surfaces oriented perpendicular to oneanother.
 37. A method of inserting an intervertebral implant in a spinecomprising: a. preparing an affected area of the spine to receive theimplant; and b. inserting a keel of an implant into the affected areafrom a lateral approach.
 38. A method of manufacturing an intervertebralimplant comprising: a. selecting a first end plate having a first keelprotruding from a first outer surface and extending between a rightlateral side and a left lateral side; b. selecting a second end platehaving a second keel protruding from a second opposed outer surface andextending between a right lateral side and a left lateral side, and c.coupling a spacer to the first end plate and the second end plate,wherein the spacer has first and second opposed curved surfaces orientedperpendicular to one another.